Firefly luciferases are enzymes that catalyze the oxidation of firefly luciferins in the presence of adenosine triphosphate (ATP), magnesium ion, and oxygen, so as to bring about light emissions from the luciferins. Thus, the firefly luciferases are broadly used for detection of ATP for the purpose of detecting bacteria and the like in food and drink.
To enhance the availability of such firefly luciferases for detection of ATP, various mutant firefly luciferases have been prepared thus far. As such mutant firefly luciferases, firefly luciferases with improved thermostability (for example, see JP Patent No. 3048466; JP Patent Publication (Kokai) No. 2000-197487 A; JP Patent Publication (Kohyo) No. 9-510610 A (1997); and JP Patent Publication (Kohyo) No. 2003-518912 A), firefly luciferases with improved substrate affinity (for example, see International Publication WO 99/02697 Pamphlet; JP Patent Publication (Kohyo) No. 10-512750 A (1998); and JP Patent Publication (Kohyo) No. 2001-518799 A), firefly luciferases with altered luminescence wavelengths (for example, see JP Patent No. 2666561 and JP Patent Publication (Kohyo) No. 2003-512071 A), firefly luciferases with improved luminescence continuity (for example, see JP Patent Publication (Kokai) No. 2000-197484 A), firefly luciferases with resistance to surfactants (for example, see JP Patent Publication (Kokai) No. 11-239493 A (1999)), and the like are known.